Energetic propellant composition containing a difluoramino binder

ABSTRACT

An improved energetic propellant charge, of the solid type useful in rockets and rocket motors, may be formulated with a system of the polymer of tetrakis(difluoramino)amyl acrylate and a large amount of hexakis(difluoramino)propyl ether if trimethylolpropane trimethacrylate and a peroxidic polymerization catalyst such as dichlorobenzoyl peroxide are used to crosslink the tetrakis(difluoramino)amyl acrylate from which the polymer is derived.

United States Patent Engelet al.

[ 51 May 16, 1972 [54] ENERGETIC PROPELLANT COMPOSITION CONTAINING ADIFLUORAMINO BINDER [72] Inventors: Lawrence J. Engel, Green Brook; JohnBrooke Gardiner, Mountainside, both of NJ.

[73] Assignee: The United States of America as represented by theSecretary of the Army [22] Filed: Apr. 30, 1970 [2]] Appl. No.: 43,618

Related US. Application Data [63] Continuation-in-part of Ser. No.671,164, Sept. 27,

1967, abandoned.

[52] US. Cl ..l49/19, 149/20, 149/42,

149/44, 149/76 [51] Int. Cl. ..C06b 11/00 [58] Field of Search 149/42,19, 44, 20, 76

Primary Examiner--Carl D. Quarforth Assistant Examiner-Stephen J.Lechert, .lr.

Attorney-Harry M. Saragovitz, Edward J Kelly, Herbert Her] and James T.Deaton [5 7] ABSTRACT An improved energetic propellant charge, of thesolid type useful in rockets and rocket motors, may be formulated with asystem of the polymer of tetrakis(difluoramino)amyl acrylate and a largeamount of hexakis(difluoramino)propyl ether if, trimethylolpropanetrimethacrylate and a peroxidic polymerization catalyst such asdichlorobenzoyl peroxide are used to crosslink thetetrakis(difluoramino)amyl acrylate from which the polymer is derived.

4 Claims, No Drawings ENERGETIC PROPELLANT COMPOSITION CONTAINING ADIFLUORAMINO BINDER CROSS REFERENCE TO RELATED APPLICATION Thisapplication is a continuation-in-part of copending ap- 5 plication, Ser.No. 671,164 filed Sept. 27, 1967 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to jet propulsion andparticularly to an improved propellant charge of the solid type usefulin rockets and rocket motors.

Modern military operations are becoming more dependent upon rocketmotors. The very nature of the operations require a motor that will givehigh and reliable performance so that lives will not be lost. A rocketmotor is heavily dependent upon a reliable propellant. A solidpropellant motor is most reliable since, once ignited, it will continueto burn until it is consumed. As the usefulness of a propellant isdependent upon the intensity of thrust created by its combustion and theconsistent reproducibility of said thrust, it has long been theobjective of those engaged in the art to find a means of increasing thethrust by means of energetic propellant compositions. This inventionprovides an energetic solid rocket propellant composition that iscapable of high and reliable performance. The polymer used as thepropellant binder must result in a propellant composition with certainmechanical and chemical properties. Among some of the more importantmechanical properties are: elongation at maximum stress and at break,stress at the maximum of stress-strain curve; tensile strength; tearstrength; and elastic recovery when the stress is removed. Since thepolymeric binder and oxidizer are in intimate contact with each otherand may be exposed to elevated temperatures for prolonged storageperiods, it is important that the polymeric binder and oxidizer possessgood mutual chemical stabilities toward each other.

The use of a peroxidic curing catalyst is well known in the art ofpropellant compositions. It is also known, but not as generally, thatthe curing catalyst assumes roles beyond that of crosslinking moleculescontaining the alkenic linkage. An undesirable side reaction of thecuring catalyst is the promotion of the degradation of the curedpropellant, probably by oxidative degradation of the polymerizedfuel-binder. As a consequence of these harmful degradations, thequantity of curing catalyst used to aid in the cure of the propellantshould be held to the minimum, the final amount being a compromisebetween the quantity necessary to achieve an adequate cure of thepolymeric binder and that which can be tolerated without unduedegradation process.

The polymer of tetrakis(difluoramino)amyl acrylate has been investigatedas a material for such binder development. It is a strong polymerreadily plasticized by several NF: compounds. However, it suffers thedisadvantage of losing strength upon adding NF liquid plasticizer andwith slight increases in temperature. Therefore, attempts have been madeto improve the strength of this acrylate-type binder.

lt is therefore an object of this invention to provide atetrakis(difluoramino)amyl type polymer with improved mechanicalproperties for use in propellant compositions.

Another object of this invention is to provide a new and improvedcomposition of matter.

A further object of this invention is to provide a polymer whichrequires low levels of both curing catalyst and crosslinking agent whenit is employed in propellant compositions.

One still further object of this invention is to provide a polymer whichhas good chemical stability with the oxidizer of the propellantcomposition in which it is employed.

SUMMARY OF THE INVENTION It has been discovered that an energeticpropellant may be formulated with a system of the polymer oftetrakis(difluoramino)amyl acrylate and a large amount ofhexakis(difluoramino)propyl ether if trimethylolpropane trimethacrylateand a peroxidic polymerization catalyst such DESCRIPTION OF THEPREFERRED EMBODIMENT The synthesis of tetrakis(difluoramino)amylacrylate is effected as follows:

Divinylcarbinol N2F-l aci'ylyl chloride 1,2,4,5-tetrakis(difluoromino)-3-an1yl alcohol acrylate,

tetrakis(difiuorarnin0)amy The polymer of tetrakis(difluoramino)amylacrylate is then formed from the monomer of tetrakis(difluoramino)amylacrylate by copolymerization with trimethylolpropane trimethylacrylate(or other crosslinker containing three functional groups) and aperoxidic polymerization catalyst. For a more detailed explanation ofthis synthesis, see U. S. Pat. No. 3,441,550.

The polymerization is deferred until the mixing of all of the propellantingredients has been carried out. Dilatometer data on the propellantsystem showed the cure to be substantially complete after 72 hours at 50C.

The synthesis of hexakis(difluoramino)propyl ether is effected byreacting 1,2-divinyl ethylene oxide dissolved in carbon tetrachloridewith N 1 at reaction temperatures in the range of to C. The NF groupbecomes linked to the carbons to give the product having the compositionCH (NF CH(NF )CH(NF )OCH(NF )CH(NF )CH (NF Of course, a suitable oxygenoxidizer, such as ammonium perchlorate, is included as an ingredient inthe propellant composition.

Similarly, a suitable fuel, such as aluminum metal, is included as aningredient in the propellant composition.

A specific example of a propellant composition that has beensuccessfully formulated and fired in both hollow grain and end burningmotors containing 10 grams of propellant is included herein forillustrative purposes only. The composition is:

COMPONENTS WT.% l-lexakis(difluoramino)propyl ether 30.7Tetrakis(difluoramino)amyl acrylate 1 1.1 Dichlorobenzoyl peroxide 0. l5 Trimethylolpropane trimethyacrylate 0.65 Ammonium perchlorate, (65microns) 46.5 Aluminum 10.2

Thus, the addition of trimethylolpropane trimethacrylate to crosslinkthe tetrakis(difluoramino)amyl acrylate has permitted the use of a largeamount of hexakis(difluoramino)propyl ether as a plasticizer while stillretaining adequate physical properties.

Obviously many modifications and variations of this invention arepossible in the light of the above teaching. It is therefore to beunderstood that, within the spirit and scope of this invention, it maybe practiced otherwise than as specifically described.

We claim:

1. A solid propellant composition consisting essentially of an ammoniumperchlorate oxidizer, a metal fuel source, at least 25 weight percentplasticizer consisting essentially of hexakis(difluoramino)propyl ether,tetrakis(difluoramino)amyl acrylate, a crosslinker of trimethylolpropanetrimethyl acrylate, and a peroxide polymerization catalyst.

2. The composition of claim 1 wherein said fuel source is aluminum.

3. The composition of claim 1 wherein said peroxidic polymerizationcatalyst is dichlorobenzoyl peroxide.

4. The composition of claim 1, wherein said oxidizer is present in anamount of about 46.5 weight percent, wherein

2. The composition of claim 1 wherein said fuel source is aluminum. 3.The composition of claim 1 wherein said peroxidic polymerizationcatalyst is dichlorobenzoyl peroxide.
 4. The composition of claim 1,wherein said oxidizer is present in an amount of about 46.5 weightpercent, wherein said metal is aluminum and is present in an amount ofabout 10.2 weight percent, wherein said plasticizer is present in anamount of about 30.7 weight percent, wherein saidtetrakis(difluoramino)amyl acrylate is present in an amount of about11.1 weight percent, wherein said crosslinker is present in an amount ofabout 0.65 weight percent, and wherein said catalyst is dichlorobenzoylperoxide and is present in an amount of about 0.15 weight percent.